tivo series 4 drive pairing?

i was wondering a couple things.

1. where on the hard drive is the software stored?
is it near the 0 sector so if i was to downsize the hard drive i would not damage the software?

and how many gig does the software use?
because i am trying a new approach to a problem i have been having is i decided to clone the original 320 gig drive onto a ssd solid state drive i have but the ssd is only 240 gig so i know some data is going to be lost and that's ok as long as it is not the software.

i decided ssd because even though trim management is not going to work since the box does not know how to use trim the drive should be faster than the oem drive.

my problem is corruption of the show when ever there is any overlap and show 1 stops and the next show starts

and unexpectedly aborting the downloads via tivo to go.

so hopefully a ssd will solve that problem.

2. are the tivo hard drives paired to the serial of the box so if i buy a box on ebay that has no hard drive or a bad power supply is the drive then not going to work?

i wonder because i would like to get a broken tivo fix it to use to salvage the shows while i let the ssd continue with the recording without missing anything.

or can i connect the drive externally and salvage the shows